Your jar will include a faces-config.xml to describes the components / renderers / validators / etc, and a taglib.tld for the tags in the META-INF directory in the jar.
For the user application, put your jar in WEB-INF/lib. Then put the taglib directive in the jsps.
There are a some aspects of packaging custom components that I don't think have been standardized yet. For example, how to include images (or other resources) with a component.